Clarification of liquids



F'. BACHMANN y CLARIFICATION OF LIQUIDS Filed Jan. 26, 1957 INVENTOR.'

ATTORNEY.

Patented 'Apr'. 9, 19440 PATENT orrlca 2,196,908 Y CLARmCATION F LIQUIDS Frank Bachmann, Chicago, Ill., assigner-to The Dorr Company, poration of Delaware Inc., New York, N. Y., a cor- Application January v26, 1937, Serial No. 122,357

2 Claims.

. 'Ihis invention relates to the clariiicationv of water in municipal -or other ltration plants where water is desired to have substantially complete clarity. A 5 Many instances are encountered where water has 50l parts of turbidityl or less per million of water. Such water is reasonablyI clear but present day public demands require water to be clearer than that,so it is the treatment of reasonably .clear water that presents a problem which this invention undertakes to solve.

This problem is met by cities taking their water from lakes and other natural water sources Where ordinary water treatment plants using sedimentation basins are not justied because of their cost. So an object of this invention is to clarify water having slight but observable turbidity without the'use of expensive sedimentation basins. i

Sand filters are usuallyused under such conditions but they have the disadvantage of requiring labor for frequent cleaning. During the cleaning operation the lter bed of necessity is a disused. Also, sand filters account for a relatively large consumption of alum or other coagulatingagent, the expense of which constitutes a substantial item of operating cost. So another object of this invention isto improve the sand lter operation by rendering it more eicient whereby fewerV cleanings thereof are required, and also whereby less alum is required to dose the water to be fed to the filter.

One of the reasons for the present degree of ineiliciency of a sand filter is the penetration into the sand bed, and the consequent blinding thereof, of the iiner solids as Well as algae. Like- Wise, unreacted alum or coagulant also goes into the sand bed. So a further object of this invention is to react all of the alum with the water before the sand bed is reached thereby. An-

other object is to occulate the ilner solids and algae in the water into ocs of a size whereby they will be deposited and rest upon the surface of the sand' bed instead of penetrating into it. If the sludge or solids can be caught more or less as a cake, layer, or blanket upon the surface of the sand bed, the sludge can be cleaned or removed readily from the sand bed, whereas if the solids penetrate the bed, the sand cleaning operation -is more tedious as well as time and labor consuming. Moreover, by eiecting upon the sand bed a mator blanket of iiocs, they in turn. form a filter medium that is quiteeffective in entrapping fresh solids carried thereinto by the water descending through the lter be'd, thus (Cl. 210-16) f adding to the emciency of the iiltration functions of the sand lter itself. Heretofore, where the water was exposed'to sedimentation, the larger ,and settleable solids were removed from the water in the settler and the etliuent with non- 5 settled iines in suspension went to the lter. So the larger solids were never available to form this mat or blanket for aiding in the'e'ntrapment of the lines and slimes. y'

To these ends, the benets oi this invention l0 may be realized by associating with a sand iilter bed without the interposition of a settler or clarifier, of a occulation system whereby par-l a ticles of turbidity in the water to be iiltered are coagulated and coagmented or amassed into 15 ilocs. Such a system may be exemplified by a tank or basin to which is fed water dosed with a coagulant by which ocs are yielded therein. In the basin by means of induced superposed oppositelyvdirected streams ocs tending to settle 20 from the upper streamare caught by the lower stream and returned to the upper stream or re-` circulated Within the same basin to bring about a maximum number of collisions between iiocs and particles of turbidity. lBy this rolling treat- 26 ment, the locs are conditioned and coagmented. Fromthis zone of treatment they are caused to drift or ilow in a mannerf'whereby they are not lharmully disintegrated, to the sand lter over which they are distributed. In the iilter, the floc- 30 ladened Water descends to the sand bed whereupon the flocs are caught by the surface of the sand bed while the water penetrates the sand bed and clarified water passes from the lter.

With these and other objects and advantages, 35 the invention is illustrated in the accompanying drawing showing the best embodiment of the invention now known to me, but the showing used in for the purpose of exemplication only,l for obviously the invention is broad enough to 40 assume other manifestations'. t

In the accompanying drawing,

Flg. 1 is a plan view of a device in which the improved method may be carried out.

Fig.- 2 is a longitudinal sectional elevation; e5 partly in section, of the structure illustrated in Fig. 1. l

Fig. 3 is a section taken Fig. 2, and

Fig. t is a section taken on the line t-t of 5d Fig. 1.

In'carrying out the improved method of clariiication, the liquid. suchas water of low turbidity, to be-clariiied, is dosed with anappropriate on the line 3 3 of coagulant, such as alum. andthen fed to a basin as -the arrow shown into the chamber I I. AtA the exit end of the chamber II is arranged a turbomixer I2, or other suitable combined mixing and pumping device. The turbo-mixer I2 is supported on and driven by the main drive shaft I8 of a motor i9 mounted on a bridge 2U spanning a portion of the chamberA II.

Leading into the chamber II is a pipe I3 through which is fed, either continually or intermittently, alum or any other suitable coagulant for dosing the water to be clarified. The exit end of the pipe I3 terminates adjacent to the turbomixer I2 and the alum or other coagulant is intimately mixed with the water to be clarified, to initiate and form fioc nuclei therein as the water is drawn from' the chamber `II by the turbomixer I2.

The intimately mixed water and coagulant is then led to and through a tank I 4 where it is gently but positively agitated during its passage toward the exit end of the tank.-

Positive gentle agitation of the dosed water is conducive to iioc coagmentation and amassment, and is performed by a plurality of paddles I5 secured to shafts I6 rotatably mounted in suitable bearings housed in the side walls of the tank I4. The shafts I6 are rotated through the medium of a sprocket chain I1 operated from any suitable source of power.

The paddles Ii' are so arranged with respect I to` each other that currents are produced in the water being acted upon. The currents near the f surface ofthe body of water in the tank I4 move generally toward the exit end of such tank, while the currents near the bottom of the tank move toward the entrance end of the tank. There are thus induced in the water superposed currents wherein oc coagmentation takes place.

At the exit end of the tank I4 is a dam 2l. Over I the top of the dam 2I the occulated water ows to a lter tank 22. The lter tank 22 is divided into two sections by a partition 23. Also the dam 2| is divided into two parts.. and associated with each part is a baille 24 which diverts the stream of fiocculated water passing over the dam 2| into the filter tank 22. Thus the water, .when it reaches the filter tank 22, is practically motionless.

f -The sections of the filter tank 22.have their y bottoms divided into a plurality of parallelly arranged units 25, the walls of each.I of which extend inwardly and downwardly to discharge openings 26. As shown, the units 25 are arranged in pairs of rows and to each pair of rows is ascomposed of a bottom layer of small stones 29,a

layer of gravel 30, and a top layer of fine sand The flocculated .water in the filter tank 22 will seep or filter through the sand filter bed. In such passage the water will be clarified -and will then pass through the` discharge'openings 26 into the pipes 21.

The ocs in the) fiocculated water will `progressively collect on the surface of the sand filter bed. As the'floc accumulates on the 4filter bed it forms a mat or blanket and provides a progressively increasing initial filtering medium overlying the sand filter bed.

I claim:

l. Apparatus for the treatment of water in order to remove turbidity therefrom comprising a liquid-holding basin having therein a partial partitioning means which includes a member pro# viding a submerged Weir and which functionally divides the basin into an agitated flocculation section and la relatively quiescent filter section that is in constant hydraulic communication with the fiocculation section through the' medium of a constantly maintained liquid ow passageway extending past the submerged Weir and by which the surface level of the liquidsin said section is constantly substantially alike except for the slight difference in elevation incident Vte the gravity iiow of liquid from the occulation section`4 into the filter section; means for delivering the liquid to be treated into the flocculation section; means for agitating liquid in the fiocculation section in a manner conducive to floc coagmentation and amassment; a filter bed of porous ltering medium disposed within the lower portion of the filter .section overlying the iioor portion of the filter section and of suchl depth that the top of 2. Apparatus for the treatment of water'acf;

cording to the claim last preceding in which the feed for incoming water is provided with means for supplying a coagulating agent to the inowing water and also with means for intimately dispersing the dosing coagulant within and throughthe filter bed is at an elevation lower than' thatof the submerged Weir; and means for conducting` out the water prior to the delivery of the thus dosed water into the fiocculation zone.

FRANK BACHMIANN. 

